a. Field of the Invention
This invention relates to an arrangement of speaker units for mid-bass, mid-range and high frequency sound reproduction systems, particularly adapted for high power output. More particularly, the invention is directed to a manifold for coupling multiple loudspeaker units, to derive high power output with desirable characteristics in the mid-bass, mid-range and high frequency regions.
b. Description of the Prior Art
Multiple loudspeakers are often used in sound applications requiring high acoustic power output (sound volume) such as theaters or arenas or for studio and stage monitoring, discotheques and the like. In many sound systems several components, such as driver/horn assemblies or cone/enclosure loudspeakers, are used for sound reproduction across the entire range of audible sound, with different devices covering the bass or low frequency range (up to 200 hertz), mid-bass and mid-range (200-2000 hertz), and high frequency (above 2000 hertz) portions of the sound spectrum.
For loud sounds or high volume it is necessary to set a large volume of air in motion to create high acoustic power. In order to move larger air volumes, the excursion of a moving diaphragm having a given cone area could be increased, but once the linear limitation of the loudspeaker suspension is reached acoustic distortion increases with increasing excursion, so that this solution to attaining high sound volume is not as desirable as using multiple loudspeakers.
Multiple loudspeakers are conventionally mounted on a front baffle board of a speaker housing or enclosure. The housing may be closed or may be provided with one or more phase-inverting ports or ducts, as in a bass-reflex type enclosure. Acoustic coupling and wave addition occurs in such structures at frequencies where the wavelengths are sufficiently greater than the distances between the individual speakers or the phase-inverting ports. However, for frequencies where the wavelengths are shorter, the use of multiple speakers may cause aberrations in the uniformity of response in various directions, due to the interference between the sound waves from the different speakers, which can cause gaps or "holes" in the frequency characteristic for particular directions toward which the sound is to be projected. U.S. Pat. Nos. 4,391,346 and 4,437,540 issued to Murikami et al. respectively on July 5, 1983, and Mar. 20, 1984, show one approach to combining the outputs of several cone-type speakers. The individual speaker units are set in the walls of a cavity behind a front baffle board or panel. The speaker units of Murikami et al. are arranged so that the sound-radiating axes of the speaker units angularly converge forward and are concentrated on a point of the central axis of the cavity just behind a front baffle panel toward which the speakers are generally aimed. Such an arrangement adversely affects sound reproduction in the mid-bass/mid-range covering approximately 200 hertz to 2,000 hertz, because at frequencies at which the wavelength is less than the spacing between the speaker units, the outputs of the individual units will not completely add, because of phase differences due to path length differences.
Another arrangement highly suitable for bass or woofer speakers is shown in copending application of R. J. Newman and D. E. Carlson, Ser. No. 834,403 entitled "High Output Loudspeaker for Low Frequency Reproduction", filed Feb. 26, 1986 assigned to the same assignee as the present application. However, this other arrangement is suitable mostly for the very low frequency range, and is not sufficiently effective in the mid-bass/mid-range.
The present invention is directed toward a solution for these drawbacks by providing a novel and unique loudspeaker manifolding system, particularly useful for mid-bass/mid-range frequencies using cone-type loudspeakers and for high frequencies using compression drivers.